https://techcrunch.com/2018/01/22/spacex-cant-test-launch-falcon-heavy-while-government-is-shut-down/

SpaceX is impacted by the ongoing U.S. Government shutdown – which is bad news both for its pending Falcon Heavy test flight, as well as for its other missions, which include imminent ISS resupply and commercial satellite launches. The Verge has confirmed that SpaceX’s dependence on U.S. Air Force support for launch operations at Cape Canaveral has held up any potential launch operations there for the private space company helmed bye Elon Musk.

Specifically, SpaceX needs the Air Force’s 45th Space Wing to oversee operations, and the government shutdown means key civilian employees of said wing are not available, which basically means the Space Wing can’t operate. This is crucial, since a big part of the Air Force unit’s job is making sure that people involved in launch operations are safe during missions.